[lldb-vscode] Use LLVM's ScopeExit to ensure we always terminate the debugger

[JDevlieghere]

Summary

Make sure we always terminate the debugger by using a RAII object.

[dblaikie]

@wallace - minor inconvenience, but approving a patch in Phabricator without any textual comment does not result in an email to the list, making it look like a patch is being committed without approval - could you include some text in your Phab approvals, as it makes it a bit easier when doing post-commit/process review?

@JDevlieghere Is it worth having a C++ RAII object that calls initialize in the ctor and terminate in the dtor? (maybe even removing the init/terminate free functions, and making them only accessible through an RAII object if that's suitable) What do the other uses of init/terminate look like/could they benefit from such refactoring?

lldb/tools/lldb-vscode/lldb-vscode.cpp

 #include <memory>
 #include <mutex>
 #include <set>
 #include <sstream>
 #include <thread>
 #include <vector>
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/Errno.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/PrettyStackTrace.h"
if (llvm::opt::Arg *comm_file = input_args.getLastArg(OPT_comm_file)) {
                       "specified\n";
       return EXIT_FAILURE;
     }
   }
 
   // Initialize LLDB first before we do anything.
   lldb::SBDebugger::Initialize();
 
+  // Terminate the debugger before the C++ destructor chain kicks in.
+  auto terminate_debugger =
+      llvm::make_scope_exit([] { lldb::SBDebugger::Terminate(); });
+
   RegisterRequestCallbacks();
 
   int portno = -1;
 
   if (input_args.hasArg(OPT_help)) {
     printHelp(T, llvm::sys::path::filename(argv[0]));
     return EXIT_SUCCESS;
   }
while (!g_vsc.sent_terminated_event) {
     if (status != lldb_vscode::PacketStatus::Success)
       return 1; // Fatal error
 
     if (!g_vsc.HandleObject(object))
       return 1;
     ++packet_idx;
   }
 
-  // We must terminate the debugger in a thread before the C++ destructor
-  // chain messes everything up.
-  lldb::SBDebugger::Terminate();
   return EXIT_SUCCESS;
 }